Energy dissipation circuit for electromagnetic injection

Abstract

An electronic control unit for regulating the air/fuel ratio of an internal combustion engine is disclosed. The electronic control unit includes an injector driver circuit which regulates the timing of the opening and closing operations of a plurality of electromagnetic solenoid injectors which input fuel to the engine. The injector driver circuit controls the injection with a pulse width modulated signal to supply an amount of fuel calculated from the operating parameters of the engine. The injector driver circuit is further provided with an energy dissipation circuit to assist in the rapid de-energization of the solenoid injectors. The energy dissipation circuit drains the energy stored in the rapidly collapsing magnetic field of a de-energized injector through a power device whose energy dissipation is controlled by the breakdown voltage of a Zener diode connected to the control terminal of the power device. The power device provides a variable conductance which dissipates an amount of energy proportional to the gain of the device times the amount of energy dissipated through the Zener diode. Preferably, the power device can be a final driver transistor used by the injector driver circuit to open and close the injectors.

What is claimed is: 
     
       1. An electronic fuel management system for regulating the air/fuel ratio of an internal combustion engine, said management system comprising: computational circuit means for calculating a fuel pulse signal whose duration is dependent upon at least one operational parameter of the internal combustion engine;   injector driver means, responsive to said fuel pulse signal from the computational circuit means, for opening and closing a plurality of solenoid operated injector valves with an injector driver signal having a leading and trailing edge; and   energy dissipation means for dissipating the energy stored in the inductance of said solenoids upon deenergization of the solenoids, wherein said energy dissipation speeds up one of the opening and closing of the valves at one of the leading and trailing edges of the injector driver signal, said energy dissipation means including:   an active power device, for dissipating said stored energy, whose conductance between its power terminals is controlled by a predetermined voltage connected to a control terminal of said power device, at least one of said power terminals electrically coupled to said inductance, wherein said predetermined voltage is generated by the collapsing field of said solenoids and causes the power device to dissipate the stored energy at a rate dependent upon the voltage and the gain of the active device.   
     
     
       2. An electronic fuel management system including an energy dissipation means as defined in claim 1 wherein: said predetermined voltage is the Zener breakdown voltage of a Zener diode connected to said control terminal.   
     
     
       3. An electronic fuel management system including an energy dissipation means as defined in claim 2 wherein: said power device is a NPN transistor with its collector connected to a current source and its emitter connected to an energization terminal of at least one of said solenoid injectors wherein said other terminal of the one injector is connected to ground.   
     
     
       4. An electronic fuel management system including an energy dissipation means as defined in claim 3 wherein: said Zener diode is connected to the base of the NPN transistor at its anode and has its cathode connected to ground.   
     
     
       5. An electronic fuel management system including an energy dissipation means as defined in claim 4 wherein: said injectors are divided into independently energized groups with each group having an associated power device and an associated Zener diode.   
     
     
       6. An electronic fuel management system including an energy dissipation means as defined in claim 5 wherein: the control terminals of each power device are connected to a single Zener diode that is the associated Zener diode for all the groups.   
     
     
       7. An electronic fuel management system including an energy dissipation means as defined in claim 6 wherein: each of said power devices has a blocking diode connected between its control terminal and said single Zener diode.   
     
     
       8. An electronic fuel management system including an energy dissipation means as defined in claim 7 wherein: said blocking diodes have their anode terminals connected to the control terminals of the associated transistors and their cathode terminals connected commonly at the anode of said Zener diode.   
     
     
       9. An electronic fuel management system including an energy dissipation means as defined in claim 8 wherein: said associated transistors further are included in said injector driver means as the final drive transistor of a driver amplifier used for opening and closing said injector valves with said injector driver signal.   
     
     
       10. An electronic fuel management system including an energy dissipation means as defined in claim 5 or 9 wherein: said injector groups include more than one injector per group and said energy dissipation means normalizes the timing of the deenergization of each group and normalizes the timing of the deenergization between different groups.